A wellsite in the Bakken Shale experienced cost savings and better data access for accurate LACT processes.
by Patrick Bartell (Valin Corporation)
November 18, 2014

The accurate allocation measurement of oil, water and gas is a constant priority for managers of surface operations, particularly with the recent oil boom in parts of the U.S. These measurements are the basis of the financial transaction between oil companies and royalty owners, keeping operations running with accurate production rates and providing insight into potential measurement problems. With newer technology available to monitor and track allocation measurement, many companies in the Bakken region have used a retrofit solution to bring their operation up to the measurement and automation standards of the 21st century. One energy company that manages a surface operation in the Bakken formation in Williston, North Dakota, recently commissioned a technical solution provider to retrofit its existing separation systems with precision automated measurement hardware and software. The project’s goal was to increase the operation’s efficiency and financial viability. This automated measurement system, combined with new installations, was designed to work with the existing separators to increase measurement accuracy and allow for improved remote operation functionality and ease of use for on-site personnel. The retrofit process was also significantly less of a financial investment for the company than replacing all of its existing separator and measurement hardware. Before the installation, operations and reservoir engineers relied on periodic manual measurements to track production and separation outputs, limiting the amount of data available to support their ability to run the operation as efficiently as possible. Applying these improvements to the surface operation provided multiple financial and operational benefits.

Existing Measurement Technology

The wellsite in North Dakota previously used manually operated separators with no measurement technology to determine the flow rates and fluid amounts produced at the surface sites. This required an operator to travel to the location of the well pads and perform manual measurements of oil and water levels in tanks.

Bridle and differential pressure transmitter on three-phase treaterImage 2. Bridle and differential pressure transmitter on three-phase treater

This type wellsite made obtaining reliable data from multiple field processing units in a timely manner costly and difficult. The intermittency and low accuracy of the data put the company at risk for unnecessary waste, poor separation, errors in field processing, reduced product quality and danger to site personnel. With its older separation measurement technology, field managers at the company were often hesitant to fully trust the allocation data readouts and did not have all the necessary data immediately available to monitor their operation. For the company, inaccurate data could have easily resulted in the under reading of valuable product. With the managers’ original hardware, a separator could malfunction and over- or under-allocate oil. This is a preventable problem that the company wanted to avoid. In addition to eliminating the cost of manually monitoring these production facil­ities, safety risks are mitigated with remote monitoring. With this unreliable measurement technology, the company also risked reduced quality of the end product. With strict standards governing processed crude oil, the company realized its need to have access to all the necessary data to determine whether the resulting product was of proper quality. In addition to these operational shortcomings, the company also received news that it must soon meet regulatory requirements regarding real-time measurement of the operation. With the company’s existing methods no longer a viable option, the company decided that retrofitting its existing hardware with automated measurement technology would be the best solution.

The Challenge

While implementing this retrofit system, the technical solutions provider was tasked with updating the oil company’s systems in a reliable way that would not interrupt current operations. All the new hardware had to be compatible with the existing systems to ensure operational viability once the installation was complete. The technical solutions provider sent a team of engineers to the Bakken wellsite to customize and install a set of retrofitted hardware and software that would deliver full function­ality with the pre-existing equipment, along with the ability to tie everything into a supervisory control and data acquisition (SCADA) system.

The Solution: Advanced Measurement Technology

The newer technology consisted of a system of Coriolis meters, level measurement, control valves and a small programmable logic controller (PLC) to capture measurement and production information at the sites, creating significant operational improvements. The new system allows for more precise measurement of oil and water at the well, and it reduces the amount of oil and water that is processed without being properly accounted for. The technology consists of a series of precision sensors that accurately measure the levels of fluids in the separation system, coupled with mechanical control valves that were supplied with either electric or pneumatic actuators. A sophisticated interface enables users to monitor and measure the output of the well more accurately and in real time and track production data from both on-site and remote terminals run by a PLC program customized for this application. The PLC can control up to four separators simultaneously, allowing operators more flexibility. Most wellsites operated by the company have a dedicated two-phase separator and three-phase heater treater with manual, float-operated valves. During the automation process, the separators were retrofitted with electrically or pneumatically actuated valves, level transmitters, oil and water density meters, and PLCs. With the automated measurement technology’s new hardware and software, important information became available to end users at the wellsite. In addition to monitoring fluid levels, the PLC allowed them to view important system information—including daily totals, monthly totals, American Petroleum Institute gravity, temperature, emergency shutdown valve status, valve position, tank levels, tubing pressure and casing pressure.

Image 3. The retrofit oil valve was installed inline with the existing valve.

The most useful feature of the new technology was the measurement and data logging of water flow rate, oil flow rate, gas flow rate and lease automatic custody transfer information (LACT). These measurements determine the amount of oil, water and gas being separated and flowing through the field processing systems. With precise mechanical valves and level control sensors, the retrofit technology provides accurate measurement of valuable processed crude oil to provide data for royalty payments and other financial transactions, such as comingling tankage on the lease. Data are also available to measure the relative productivity and value of the wellsite operation. For the field managers and other end users, the technology provides options to:

  • View oil flow rate
  • Control freshwater and saltwater pumps
  • Set the variable frequency drive to run permissive
  • View other SCADA information

With a complete monitoring and measurement system attached to its existing separation technology, the efficiency and accuracy of the company’s well operations significantly increased.

Results

The oil company gained several advantages from adding the automated measurement technology to its Bakken Shale wellsites. With access to automatic data from an increased number of locations, the company decreased operational costs, leading to significant savings. The efficiency of the operation was also improved because of technical adjustments made possible with information gathered by the tech­nology. Finally, the company has access to better real-time data about the state of the operation, enabling its field managers to detect potential errors before they become more serious problems. As a result of the innovative, customized set of advanced measurement tools added to its wellsites, the oil company now achieves higher productivity and financial efficiency.